It is known that aminoalkyl-thiol derivatives of the formula II ##STR3## containing a sulfhydryl group--wherein R.sup.3 is hydrogen or carboxamidino
R.sup.4 is hydrogen or carboxy and PA1 B is hydrogen or carboxamidino, provided that at least two of R.sup.3 and R.sup.4 and B are hydrogen- PA1 R.sup.2 is hydrogen or a carboxy group which can be esterified with aryl-(C.sub.1-4)alkoxy, PA1 A is --SO.sub.2 OH or --O--PO(OH).sub.2, PA1 n is 1, 2 or 3 and PA1 m represents 2, 3 or 4 PA1 AET=aminoethyl-isothiuronium-chloride-hydrochloride Litoralon=.gamma.-glutamyl-taurine PA1 GABA-T=.gamma.-aminobutyryl-taurine PA1 GABA-E=.gamma.-aminobutyryl-ethanolamine-phosphate
and pharmaceutically acceptable acid addition salts thereof are the most effective radiation-protective substances known heretofore (Knoll J., Gyogyszertan, Medicina, 1965, page 540). As examples for the above substances cysteine, cysteamine, aminoethyl-isothiuronium-chloride-hydrochloride, aminoethyl-isothiuronium-bromide-hydrobromide and mercaptoethyl-guanidine may be mentioned. Though the radiation protective activity of the above substances is significant in animal tests, the practical therapeutic utilization thereof is rather difficult because of the toxicity of their effective dose or because this effective dose is rather close to the toxic range.
Some of the characteristics of some most important radiation protective active ingredients are shown in Table 1.
TABLE 1 ______________________________________ Radiation protective LD.sub.50 p.o. dose Therapeutic Active ingredient mg./kg. mg./kg. index ______________________________________ cysteine-hydrochloride 2500 1900 1.31 aminoethyl-isothiuronium- 1200 1000 1.20 bromide-hydrobromide aminoethyl-isothiuronium- 710 400 1.78 chloride-hydrochloride mercaptoethyl-guanidine 350 200 1.75 ______________________________________
The data of the table show that the toxic and therapeutic doses are close to each other.
With the increasing use of radioactive isotopes the probability of radiation injuries increases as well. As a consequence radiation-protective pharmaceutical compositions are needed more and more. In this field both compositions suitable for curing radiation injuries and compositions suitable for treating humans or animals prior to irradiation in order to increase the tolerated dose by the patients for cases of higher radiation doses are desired.